Practice!

Sample Problem

Sid melts two iron cubes with side length 10 cm and 8 cm into a big rectangular solid. If the cross section of the big rectangular solid is a square with side length 4 cm, then what is its length?

  cm

Solution

The total volume of the 2 iron boxes is 103 + 83 = 1512 cm3. If the cross section is a square with side length 4 cm, then that means it is also one of the faces. One face must have an area of 4 × 4. So we have 4 × 4 × length = 1512, so the length of the big box is therefore 1512 ÷ (4 × 4) = 94.5 cm.